JP5397432B2 - Rotating electrical machine drive system - Google Patents

Description

  The present invention relates to a drive system for a rotating electrical machine that functions as one of driving driving sources for a vehicle, and more particularly, to a discharge technique for a smoothing capacitor provided in the drive system.

  2. Description of the Related Art Conventionally, an electric vehicle equipped with a rotating electrical machine, for example, a hybrid vehicle or an electric vehicle, is widely known as one of travel driving sources. Such an electric vehicle is usually provided with an inverter that supplies AC power to the rotating electrical machine, a battery connected to the inverter, and a smoothing capacitor that smoothes the voltage between the terminals of the inverter. In such a vehicle, at the time of a vehicle collision, it is desirable to switch the switching element of the inverter to discharge the electric charge of the smoothing capacitor. In order to reliably perform this discharge, Patent Document 1 discloses a technique for switching control of an inverter so as to discharge a charge of a smoothing capacitor when a vehicle collision is predicted. According to this technique, since the inverter can be driven for discharging before the drive circuit of the inverter is destroyed due to a collision, the electric charge of the capacitor can be reliably discharged.

JP-A-2005-020952 JP 2005-094883 A JP 2006-020450 A

  However, during such discharge treatment, if the rotating electrical machine is rotating, a counter electromotive voltage is generated, and there is a problem that the discharge cannot be performed or the discharge takes time. In particular, when the drive shaft comes off due to a vehicle collision or when the vehicle rolls over, such a problem is likely to occur because the motor continues to rotate even if the vehicle stops.

  In Patent Documents 2 and 3, when a vehicle collision is detected, the switching element on the upper arm side of the inverter is turned off and the switching element on the lower arm side is turned on to generate the braking force of the vehicle. Thereafter, a technique is disclosed in which all the switching elements are turned on to discharge the electric charge remaining in the smoothing capacitor. Thus, prior to the discharge, a braking force is generated and the rotational speed of the rotating electrical machine is reduced, whereby the time from the collision to the completion of the discharge can be further shortened.

  However, the techniques described in Patent Documents 2 and 3 have not been able to efficiently reduce the rotational speed of the rotating electrical machine. As a result, even with the techniques of Patent Documents 2 and 3, it may take time to complete the discharge.

  Therefore, an object of the present invention is to provide a drive system for a rotating electrical machine that can discharge a smoothing capacitor more quickly.

The drive system of the present invention is a drive system for a rotating electrical machine that functions as one of the travel drive sources of a vehicle, and is supplied from a collision detection means for detecting the collision of the vehicle or the possibility of a collision, and a DC power source. An inverter that converts direct current power into alternating current power and outputs it to the rotating electrical machine, a smoothing capacitor that smoothes a voltage between terminals of the inverter, and the direct current power source when the collision or the possibility of the collision is detected with interrupting the power output from the rotational speed reduction control lines stomach to below a first threshold value defined in advance the rotational speed of the rotary electric machine, the smoothing capacitor if the rotational speed is below said first threshold value Control means for performing discharge control for controlling the inverter so as to discharge the electric charge stored in the control circuit, wherein the control means is the rotational speed of the rotating electrical machine in the rotational speed reduction control. For high second-threshold value than the first threshold value, and one of the switching elements of the arm or the lower arm is turned on only one phase on the inverter, line physician an phase ON control for all the other switching element off When the rotational speed of the rotating electrical machine is equal to or lower than the second threshold value and exceeds the first threshold value, the switching element on the upper arm or the lower arm of the inverter is turned off for all three phases, and the other switching element is turned on. Three-phase on control is performed in which all three phases are turned on .

  In another preferred aspect, the second threshold value is the rotation speed when the magnitude relationship between the drag torque generated during the one-phase on control and the drag torque generated during the three-phase on control is reversed.

  According to the present invention, since the one-phase on control is executed in the rotation speed range higher than the second threshold value, the rotation speed can be reduced more quickly, and thus the time from the collision detection to the completion of discharge is further shortened. be able to.

It is a figure which shows the structure of the drive system which is embodiment of this invention. It is a figure which shows the relationship between drag torque and rotation speed. It is a flowchart which shows the flow of control after a collision detection. It is a figure which shows the mode of a change of the rotation speed at the time of performing only this embodiment and three-phase ON control.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a drive system for a rotating electrical machine 10 according to an embodiment of the present invention. This drive system is mounted on a vehicle equipped with the rotating electrical machine 10 as one of the travel drive sources, for example, a hybrid vehicle or an electric vehicle, and controls driving of the rotating electrical machine 10.

  The drive system includes a DC power supply 16, a smoothing capacitor 14, an inverter 12, a collision detection device 22, a control unit, and the like. The rotating electrical machine 10 driven by this drive system functions as a motor that generates torque for driving the driving wheels of the vehicle, while generating regenerative power by receiving the rotational force from the driving wheels during braking of the automobile. The rotating electrical machine 10 also functions as a generator.

  DC power supply 16 includes a power storage device (not shown), and outputs a DC voltage between power supply line VL and earth line SL. For example, the DC power supply 16 can be configured to convert the output voltage of the secondary battery and output it to the power supply line VL and the earth line SL by a combination of the secondary battery and the buck-boost converter. In this case, the step-up / down converter is configured to be capable of bidirectional power conversion, and the DC voltage between the power supply line VL and the earth line SL is converted to the charging voltage of the secondary battery.

  System relay SR1 is connected between the positive electrode of DC power supply 16 and power supply line VL, and system relay SR2 is connected between the negative electrode of DC power supply 16 and ground line SL. System relays SR1 and SR2 are turned on / off by a signal from computer 18 for driving MG. A smoothing capacitor 14 is connected between the power supply line VL and the earth line SL.

  Inverter 12 includes a U-phase arm 30, a V-phase arm 32, and a W-phase arm 34. U-phase arm 30, V-phase arm 32, and W-phase arm 34 are provided in parallel between power supply line VL and ground line SL.

  U-phase arm 30 includes switching elements Q1, Q2 connected in series. Similarly, the V-phase arm 32 includes two switching elements Q3 and Q4 connected in series, and the W-phase arm 34 also includes two switching elements Q5 and Q6 connected in series. Further, diodes D1 to D6 that flow current from the emitter side to the collector side are connected between the collectors and emitters of the switching elements Q1 to Q6, respectively. As the switching element in this embodiment, for example, an IGBT (Insulated Gate Bipolar Transistor) is applied. The switching elements Q <b> 1 to Q <b> 6 are subjected to on / off control, i.e., switching control, in response to a switching control signal from the MG driving computer 18. Of the plurality of switching elements Q1 to Q6, the switching elements Q1, Q3, and Q5 connected to the high voltage side (plus terminal side) of the secondary battery serve as the upper arm (high voltage side arm) of the inverter 12. The switching elements Q2, Q4, and Q6 that are configured and connected to the low voltage side (minus terminal side) of the secondary battery constitute a lower arm (low voltage side arm).

  An intermediate point of each phase arm is connected to each phase end of each phase coil of rotating electrical machine 10 via a conductive wire. That is, the rotating electrical machine 10 is a three-phase permanent magnet motor, and is configured by connecting one end of three coils of U, V, and W phases in common to a neutral point. The other end of the U-phase coil is connected to the intermediate point of the IGBT elements Q1 and Q2 via the conductive wire, and the other end of the V-phase coil is connected to the intermediate point of the IGBT elements Q3 and Q4 via the conductive wire. Are connected to intermediate points of IGBT elements Q5 and Q6 through conductive lines, respectively.

  A current sensor 24 is inserted in the U phase and the V phase of the conductive wires. The current sensor 24 detects current flowing in the U phase and V phase of the rotating electrical machine 10. The current detection value by the current sensor 24 is sent to the MG drive computer 18. In addition, since the sum of the U-phase, V-phase, and W-phase motor currents Iu, Iv, and Iw (instantaneous values) is zero, the MG drive computer 18 determines the W-phase motor current from the U-phase and V-phase motor currents. The motor current Iw is calculated.

  Further, the rotary electric machine 10 is provided with a position sensor 26 that detects a rotation angle of a rotor (not shown). The rotation angle detected by the position sensor 26 is sent to the MG drive computer 18.

  The MG drive computer 18 functions as a control unit together with the HV-ECU 20 described later, and controls the switching elements Q1 to Q6 of the inverter 12 while switching the system relays SR1 and SR2 on / off. The MG drive computer 18 receives an operation command for the rotating electrical machine 10 from the HV-ECU 20. This operation command includes an operation permission / prohibition instruction for the rotating electrical machine 10, a torque command value, a rotation speed command, and the like. The MG drive computer 18 controls the switching operation of the switching elements Q1 to Q6 so that the rotating electrical machine 10 operates according to the operation command from the HV-ECU 20 by feedback control based on the detection values of the current sensor 24 and the position sensor 26. A switching control signal is generated.

  For example, when an operation instruction for the rotating electrical machine 10 is issued by the HV-ECU 20, the MG driving computer 18 performs switching so that each phase motor current corresponding to the torque command value of the rotating electrical machine 10 is supplied. Generate control signals. Further, at the time of regenerative braking of the rotating electrical machine 10, the MG drive computer 18 generates a switching control signal so as to convert the AC voltage generated by the rotating electrical machine 10 into a DC voltage. Further, when the HV-ECU 20 instructs the discharge of the smoothing capacitor 14, the MG driving computer 18 turns off the system relays SR1 and SR2 and generates a switching control signal for discharging. Will be described in detail later.

  The HV-ECU 20 (Electronic Control Unit) calculates an operation permission / prohibition instruction, a torque command value, a rotation speed command, and the like of the rotating electrical machine 10 according to the driving state of the vehicle, and outputs them to the MG drive computer 18. The HV-ECU 20 receives a collision detection signal from the collision detection device 22. The collision detection device 22 includes a radar sensor and a pre-crash sensor ECU mounted on the vehicle. The radar sensor measures the collision speed (that is, the relative speed between the obstacle and the host vehicle) between the obstacle (including another vehicle) and the vehicle (the host vehicle) and the distance between the obstacle and the host vehicle. As this radar sensor, for example, a millimeter wave radar for radar cruise can be used. These measurement signals are transmitted to the pre-crash sensor ECU. The pre-crash sensor ECU determines the possibility of a collision based on the transmitted signal, and if there is a possibility of a collision, the pre-crash sensor ECU collides with the HV-ECU 20. Send a detection signal. When receiving the collision detection signal, the HV-ECU 20 instructs the MG driving computer 18 to discharge the electric charge accumulated in the smoothing capacitor 14.

  Next, the control by the MG drive computer 18 during discharge will be described in detail. As described above, when receiving the collision detection signal, the HV-ECU 20 instructs the MG driving computer 18 to discharge the electric charge accumulated in the smoothing capacitor 14. Upon receiving this instruction, the MG drive computer 18 turns off the system relays SR1 and SR2 and cuts off the supply of power to the inverter 12.

  The MG drive computer 18 also executes discharge control for controlling the drive of the inverter 12 and discharging electric charges from the smoothing capacitor 14. In the discharge control, for example, by flowing a d-axis current through the rotating electrical machine 10, in other words, by energizing the coil of the rotating electrical machine 10 so as not to generate torque in the rotating electrical machine 10, the electric charge of the smoothing capacitor 14 is discharged. Thus, the inverter 12 is controlled. Thus, by actively consuming electric power, the smoothing capacitor 14 can be discharged quickly.

  However, during this discharge control, if the rotating electrical machine 10 is rotating, a back electromotive voltage is generated, and there is a problem that it cannot be discharged or takes time. In particular, when the drive shaft comes off due to a collision or the vehicle rolls over, the rotating electrical machine 10 often continues to rotate at a high speed even if the vehicle stops.

  Therefore, in the present embodiment, prior to the discharge control, the rotational speed reduction control for reducing the rotational speed of the rotating electrical machine 10 is also performed. In this rotational speed reduction control, one-phase on control or three-phase on control is executed according to the rotational speed of the rotating electrical machine 10.

  The three-phase ON control is performed by the upper arm connected to the high voltage side (plus terminal side) or the lower arm connected to the low voltage side (minus terminal side) of the switching elements Q1 to Q6 of the inverter 12. This control is to turn on one of the switching elements for all three phases. Therefore, in the case of three-phase on control, all the upper arm three phases are on and all the lower arm three phases are off, or all the lower arm three phases are on and all the upper arm three phases are off.

  Further, the one-phase on control is connected to the upper arm connected to the high voltage side (plus terminal side) or the low voltage side (minus terminal side) among the switching elements Q1 to Q6 of the inverter 12. In this control, only one phase of the switching element of the lower arm is turned on. Therefore, in the case of one-phase on control, one upper arm phase is on and all other two phases and lower arm of the upper arm are off, or one lower arm phase is on and the other two phases and upper arm of the lower arm. All three phases are turned off.

  When the one-phase on control and the three-phase on control are performed, the rotating electrical machine 10 generates a rotation resistance, that is, a so-called “drag torque” accompanying the rotation. In the present embodiment, by actively generating this drag torque, the number of rotations of the rotating electrical machine 10 can be quickly reduced, and thus rapid discharge is possible.

  Here, the drag torque changes according to the rotational speed. FIG. 2 is a graph showing the relationship between the drag torque generated when the one-phase on control and the three-phase on control are performed and the rotation speed. In FIG. 2, the solid line indicates the drag torque during the three-phase on control, and the broken line indicates the drag torque during the one-phase on control. The drag torque is represented by a negative value in order to distinguish it from torque generated during powering control of the rotating electrical machine 10.

  As is apparent from FIG. 2, the drag torque during the three-phase ON control increases sharply at the rotational speeds R1 to R2 that are in the low rotational speed range, then decreases sharply, and gradually decreases after the rotational speed R2. Continues to. Therefore, the drag torque during the three-phase ON control takes a relatively high value at the rotation speeds R1 to R2 in the low rotation speed range, and takes a relatively low value after the rotation speed R2.

  On the other hand, the drag torque at the time of one-phase on control increases slowly until it reaches a relatively high rotation speed R3 (R3> R2), and after reaching an extreme value at the rotation speed R3, it slowly decreases. Decrease.

  When comparing the drag torque at the time of one-phase on control and that at the time of three-phase on control, the drag torque at the time of three-phase on control is higher in the low rpm range until reaching the rpm R2. In the high rotation speed range exceeding R2, the drag torque during the one-phase on control is higher. In the present embodiment, paying attention to the relationship between the drag torque and the rotational speed, control for obtaining a higher drag torque is executed.

  Specifically, in the present embodiment, the number of rotations at which the rotation of the rotating electrical machine 10 can be regarded as substantially zero, in other words, the back electromotive voltage generated along with the rotation is small, and discharge by switching control can be performed within a specified time. The rotation speed R1 is set as the first threshold value. Further, the rotation speed R2 at which the magnitude relationship between the drag torque during the one-phase on control and the drag torque during the three-phase on control is reversed is set as the second threshold value. If the rotational speed reduction control of the rotating electrical machine 10 is necessary for discharging the smoothing capacitor 14, first, the rotational speed of the rotating electrical machine 10 is acquired. When the obtained rotational speed exceeds the second threshold value R2, one-phase on control is performed, and when it is equal to or less than the second threshold value R2, three-phase on control is performed. When the rotational speed of the rotating electrical machine 10 is equal to or less than the first threshold value R1, the discharge control of the smoothing capacitor 14, that is, the switching control of the inverter 12 is performed so that the coil of the rotating electrical machine 10 is energized so as not to generate torque. To do. By setting it as this structure, after the collision of a vehicle, the rotation speed of the rotary electric machine 10 can be reduced more rapidly, and discharge control can be started more rapidly. As a result, the time from the occurrence of a vehicle collision to the completion of discharge can be shortened.

  Next, the discharge process at the time of the collision in this embodiment is demonstrated with reference to FIG. FIG. 3 is a flowchart showing the flow of processing from collision detection to discharge completion in the present embodiment. As shown in FIG. 3, when the HV-ECU 20 receives a collision detection signal (S10), the HV-ECU 20 instructs the MG drive computer 18 to execute control corresponding to the collision. Receiving this instruction, the MG drive computer 18 turns off the system relays SR1 and SR2, and cuts off the supply of power to the inverter 12 (S12).

  Subsequently, the rotational speed of the rotating electrical machine 10 is confirmed, and it is confirmed whether or not the rotational speed is equal to or less than the second threshold value R2 (S14). As a result of confirmation, when the rotation speed exceeds the second threshold value R2, among the switching elements of the inverter 12, only one phase of the upper arm or one phase of the lower arm is turned on. One-phase on control for turning off the switching element is executed (S16).

  On the other hand, if the number of revolutions is equal to or smaller than the second threshold R2 as a result of the confirmation, it is subsequently confirmed whether or not the number of revolutions is equal to or smaller than the first threshold R1 (S18). As a result of confirmation, when the rotation speed exceeds the first threshold value R1, among the switching elements of the inverter 12, only the three-phase portion of the upper arm or the three-phase portion of the lower arm is turned on. Three-phase on control for turning off the switching element is executed (S20).

  Further, when the rotational speed is equal to or less than the first threshold value, in order to energize the coil of the rotating electrical machine 10 so that the d-axis current flows in the rotating electrical machine 10, in other words, without generating torque in the rotating electrical machine 10, Switching control of the inverter 12 is performed, and discharge control for discharging the smoothing capacitor 14 is executed (S22).

  When the one-phase on control and the three-phase on control are performed, periodically check the rotation speed of the rotating electrical machine 10, that is, return to step S14 or step S18, and perform control according to the obtained rotation speed. Run.

  As is clear from the above description, in the present embodiment, the rotational speed reduction control for reducing the rotational speed of the rotating electrical machine 10 is executed prior to the discharge control. The effect of such a configuration will be described in comparison with a case where only the three-phase on control is executed to reduce the rotational speed. FIG. 4 is a graph showing changes in the rotational speed of the rotating electrical machine 10 since the rotational speed reduction control is started. In FIG. 4, the solid line L1 indicates the change in the rotation speed in the present embodiment, and the broken line L2 indicates the change in the rotation speed when only the three-phase on control is performed without performing the one-phase on control. Further, in the solid line L1 indicating the rotation speed change in the present embodiment, the thick line portion indicates the execution period of the one-phase on control, and the thin line portion indicates the execution period of the three-phase on control.

  When only the three-phase on control is used, the three-phase on control is executed immediately after the collision is detected, in other words, even in a region where the rotational speed of the rotating electrical machine 10 is relatively high. Since the drag torque is small in the high rotation speed region in the three-phase ON control, in the case of only the three-phase ON control, it takes time until the rotation speed reaches the second threshold value R2, as shown in FIG. After reaching the second threshold value R2, a high drag torque is obtained, so the rotational speed decreases sharply. However, since it takes time to reach the second threshold value R2 after the collision is detected, as a result, the time from the detection of the collision to the arrival of the first threshold value R1 at which discharge control is allowed becomes longer. Tend to.

  On the other hand, in the present embodiment, the one-phase on control is executed immediately after the collision is detected. The one-phase on control has a high drag torque in the high rotation speed range. Therefore, according to the present embodiment, the number of revolutions rapidly decreases immediately after the collision is detected. When the rotational speed reaches the second threshold value R2, the control is switched to the three-phase on control in which the drag torque in the low rotational speed range is high. As a result, after the rotation speed reaches the second threshold value R2, the rotation speed decreases more rapidly and can quickly reach the first threshold value R1.

  That is, as in this embodiment, by switching between the one-phase on control and the three-phase on control according to the rotation speed, the discharge can be completed more quickly than when only the three-phase on control is used. Can do.

  In addition, as in this embodiment, by generating drag torque as a one-phase on control or three-phase on control at the time of a collision, the inertial running of the vehicle after the collision can be reduced, and the vehicle can be operated more safely. It can be stopped.

  In the present embodiment, the rotation speed R2 when the magnitude relationship between the drag torque generated during the one-phase on control and the drag torque generated during the three-phase on control is reversed is set as the second threshold value. However, it is not necessary to strictly set the rotation speed R2 as the second threshold value, and there may naturally be a slight error. However, even in that case, it is desirable that the second threshold value is higher than the rotational speed R2.

  DESCRIPTION OF SYMBOLS 10 Rotating electrical machine, 12 Inverter, 14 Smoothing capacitor, 16 DC power supply, 18 Driving computer, 22 Collision detection device, 24 Current sensor, 26 Position sensor.

Claims (2)

A drive system for a rotating electrical machine that functions as one of the traveling drive sources of a vehicle,
Collision detection means for detecting the collision of the vehicle or the possibility of collision;
An inverter that converts DC power supplied from a DC power source into AC power and outputs the AC power to the rotating electrical machine;
A smoothing capacitor for smoothing a voltage between terminals of the inverter;
When the collision or the possibility of the collision is detected, the power output from the DC power supply is cut off, and the rotation speed reduction control is performed so that the rotation speed of the rotating electrical machine is equal to or less than a predetermined first threshold value. Control means for performing discharge control for controlling the inverter to discharge the electric charge stored in the smoothing capacitor when the rotational speed is less than or equal to the first threshold ;
With
In the rotation speed reduction control, when the rotation speed of the rotating electrical machine exceeds a second threshold value that is higher than the first threshold value, the control means sets one switching element of the upper arm or the lower arm of the inverter only for one phase. Turn on all the other switching elements have a row one phase oN control for turning off, the rotational speed of the rotary electric machine is equal to or less than the second threshold value, and when the first threshold exceeded, the arm or the lower arm on the inverter Three-phase on control is performed to turn off one switching element for all three phases and turn on the other switching element for all three phases.
A drive system for a rotating electrical machine. The rotating electrical machine drive system according to claim 1 ,
The drive system for a rotating electrical machine, wherein the second threshold value is a rotation speed when the magnitude relationship between the drag torque generated during the one-phase on control and the drag torque generated during the three-phase on control is reversed.

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